The disclosure relates to a glass article. More particularly, the disclosure relates to an aluminosilicate glass article having an outer layer under compressive stress.
When used in applications such as displays and cover glasses for electronic devices such as televisions, telephones, and entertainment devices, glass is sometimes strengthened by either thermal or chemical means. Such strengthening typically involves creating a layer at the surface of the glass that is under compression. This layer prevents flaws caused by impact of an object with the glass from propagating into the bulk of the glass, thus causing cracking and/or breakage.
One such means of chemically strengthening glass is ion exchange. Glass undergoes stress relaxation during ion exchange. Such stress relaxation can be mitigated by reducing the temperature at which ion exchange is carried out. However, reducing temperature decreases the rate and the depth to which such exchange takes place to such an extent so as to make such temperature reduction impractical. Annealing the glass prior to ion exchange tends to increase the compressive stress, but it also decreases the rate of ion exchange.